It has been proposed that in the future wireless communications networks will consist of more than one radio access technology, such as WCDMA (wideband code division multiple access), GSM/EDGE (global system for mobile communication) or the like. By exploiting the different radio access technologies, the network as a whole can take advantage of the coverage and capacity characteristics of each technology. This can result in a more economic solution and provide the most appropriate radio bearers for a variety of different services.
In the known radio access networks the management of the radio resources between the systems is performed in a distributed way. The radio network controllers of the different systems manage the radio resources of each system independently. The efficiency of the resource management functions is limited by the area under the control of the radio resource controllers of the respective systems.
It has been appreciated by the inventors that in order to utilise the existing resources most efficiently, it will be necessary to manage the traffic within the different systems. The prior art arrangement with the resources being controlled by the radio network controllers of the respective systems is a particular problem with the making of handover decision between the systems. This is because the information that can be taken into account to perform the handover is limited to the resources under the control of each radio resource controller. Within a single system, the main limitation is the small amount of information that is possible to be exchanged between different radio resource controllers. This makes the management of the radio resources in the radio resource controller border areas difficult as the knowledge of the cells under control of the neighboring radio resource controller(s) is limited. In a multi-system environment the information available from the cells of another radio access system is even more restricted and there is no standardised way to check the status of a cell in another system. Moreover, if such an interface would be standardised between for example two known radio resource controllers, a new radio access system that could be introduced later would need separate interfaces to all relevant radio resource controllers.
An additional problem is that the separate operation and maintenance of multiple systems is not cost-efficient and could result in low resource usage and poor network quality.
In 3rd generation wireless communications networks a large variety of different services can be provided to an end user. Contrary to existing 2nd generation networks a continuous coverage or Quality of Service (QoS) cannot be guaranteed for all services everywhere in the cell because of higher signal-to-interference ratios demanded by high bit rate 3rd generation services. If a cell to which a call is allocated, handed over or the like does not support the required quality of service, this may mean that the service in question cannot be supported or supported adequately.